The present invention is concerned with a process for the removal of ethanol from drinks produced by fermentation by means of extraction with the help of compressed carbon dioxide.
There is a general need substantially to remove alcohol from alcoholic drinks which have been produced by the alcoholic fermentation of sugar-containing aqueous liquids without negatively influencing the flavour quality of the drinks initially used. Examples of such alcoholic drinks include wine, fruit wine, for example cider, sparkling wine and sekt, as well as beer.
A number of processes is already known which are concerned with the production of alcohol-reduced or alcohol-free drinks but all of them involve certain disadvantages.
The older processes essentially use distillation or membrane separation for the removal of the alcohol in which case the obtaining of drinks substantially freed from alcohol with an alcohol content of less than 0.5% by volume give rise to certain difficulties which, in particular, are due to the fact that these processes display an insufficient separating effect between the ethanol, on the one hand, and the readily volatile aroma and flavour materials, on the other hand. Furthermore, in the case of the distillation processes, because of the comparatively high temperatures used, it can result in undesirable damage to the aroma and flavouring materials.
Recently, processes for the removal of alcohol by means of extraction with the help of compressed gases, for example carbon dioxide, have also been described. Thus, in Federal Republic of Germany Patent Specifications Nos. 29 02 067 and 30 24 055, it has been suggested to remove the alcohol with help of liquid or supercritical carbon dioxide and subsequently to separate it off from the carbon dioxide by decompression. However, with these processes it is only possible to reduce the alcohol content to 1 to 2% by volume. This also applies to the process according to Federal Republic of Germany Patent Specification No. 29 12 316 in which only partly fermented drinks (young beer or young wine) are treated with liquid carbon dioxide and the so-treated drinks are then subjected to a post-fermentation.
Low-alcohol drinks can be produced with the help of the process according to European Patent Specification No. 0,077,745 which is carried out in two steps. In the first step, the aromatic materials are extracted with liquid carbon dioxide, i.e. at subcritical pressure, and, in the second step, the alcohol is extracted. Subsequently, the aroma fraction is again mixed with the dealcoholated drink. The sharp separation of ethanol and aroma materials hereby give rise to particular problems, i.e. the two objects of removing the alcohol as far as possible and the maintenance of the flavour and aroma materials in the drink, can only be accomplished with difficulty.
Therefore, in Federal Republic of Germany Patent Specification No. 33 13 530, it is suggested, after removal of the alcohol with liquid or supercritical solvents, to pass the ethanol-containing solvent phase over an adsorption agent, for example active carbon. However, this process is rather laborious because the adsorption agent must again be regenerated. Furthermore, it cannot be excluded that valuable aroma materials are also adsorbed and thus are lost.
Also laborious is the process according to Federal Republic of Germany Patent Specification No. 35 42 757 in which the starting drinks are first subjected to a high pressure extraction with carbon dioxide in order to obtain an alcoholic fraction enriched with aroma materials, then the alcohol content of the remaining drink is reduced by vacuum distillation in a fractionation column and, at the same time, an aroma fraction is obtained with a higher boiling point than ethanol and subsequently the two aroma fractions are again added to the alcohol-reduced remaining drink.